Planets made of diamonds may be scattered across the universe

14 Sep 2020

Image: © kentoh/

Carbon-rich exoplanets may be made from diamonds and silica, according to new research.

With our ability to determine what a distant exoplanet is made from getting better all the time, a team of researchers from Arizona State University (ASU) and the University of Chicago has found a rather intriguing possibility when it comes to carbon-rich planets.

Writing in The Planetary Science Journal, the team said that these planets, under the right circumstances, could be made of diamonds and silica.

Typically, stars and planets form from a cloud of cosmic gas. A planet that forms with a lower carbon to oxygen ratio – such as Earth – will be made of silicates and oxides, with a very low diamond content of approximately 0.001pc. However, exoplanets with a higher carbon to oxygen ratio than Earth are much more likely to be carbon-rich.

In this latest research, the team hypothesised that these carbon-rich exoplanets could convert the carbon to diamond and silicate, if water were present, creating a diamond-rich composition. With no access to these distant planets, the research team recreated the interior of carbide exoplanets using high heat and pressure from diamond anvil cells.

Little chance of life

Using this method, silicon carbide was immersed in water and compressed between diamonds at extreme pressures and the reaction was monitored using laser heating and x-ray measurements.

The test confirmed the team’s theory as the resulting heat and pressure turned the silicon carbide into diamonds and silica. However, in the search for potential extraterrestrial life, the discovery shows these planets have a lack of geological activity, which may prevent atmospheres forming that could sustain life.

“These exoplanets are unlike anything in our solar system. Regardless of habitability, this is one additional step in helping us understand and characterise our ever-increasing and improving observations of exoplanets,” said lead author Harrison Allen-Sutter of ASU.

“The more we learn, the better we’ll be able to interpret new data from upcoming future missions like the James Webb Space Telescope and the Nancy Grace Roman Space Telescope to understand the worlds beyond on our own solar system.”

Colm Gorey was a senior journalist with Silicon Republic